A sensitive, rapid, accurate and inexpensive assay for acid neuraminidase will be devised for the postnatal and prenatal diagnosis of sialidosis, an autosomal recessive human disease due to deficiency of acid neuraminidase. Heterozygote identification will also be made more rapid and accurate with this assay. Human acid neuraminidase will be characterized and possible isoenzymes will be studied. Attempts will be made to purify the enzyme to determine its physical properties. The nature of the mutation in sialidosis will be determined. The chemical nature of the storage material in sialidosis will be defined in an attempt to relate symptoms to tissue storage.